Effects of Al addition on the microstructure, mechanical properties and thermal conductivity of high pressure die cast Mg–3RE–0.5Zn alloy ultrathin–walled component

Abstract

Strength and heat dissipation capability are the key parameters for metal materials used as the structural components of 5G stations and smartphones, while balancing the high strength and high thermal conductivity is still a long-term challenge. In the present study, we attempted to achieve high–thermal–conductivity Mg alloys combined with high strength for high pressure die cast (HPDC) ultrathin-walled components. The effects of Al addition on the microstructure, tensile properties, thermal conductivity, and electrical conductivity of HPDC Mg–3RE–0.5Zn (wt%) alloy were investigated and discussed carefully. We found that the HPDC Mg–3RE–0.5Zn showed the highest thermal conductivity of 143.6 W(m·K)−1 and electrical conductivity of 18.9 MS·m−1. With the increasing Al addition, the thermal conductivity and electrical conductivity gradually decreased while still kept a high level of 126.1–117.8 W(m·K)−1 and 17.5–16.3 MS·m−1. Furthermore, Al addition simultaneously improved the strength and elongation of HPDC Mg–3RE–0.5Zn alloy, where the HPDC Mg–3RE–0.5Zn–2Al alloy exhibited the best tensile properties with yield strength, ultimate tensile strength, and elongation of 156 MPa, 240 MPa, and 10.8%, respectively. The Al addition modified the intermetallic phases from continuous networked Mg12RE to discontinuous blocky Al2RE and/or lamellar Al11RE3 phases, which contributed to enhancing tensile properties. The results will be helpful for developing high performance HPDC Mg alloys and extending their practical application.